The Animal Core is essential for best serving the animal testing needs of the different projects. The cost effectiveness of this type of core service is readily realized by having well-equipped facilities and property trained personnel that are dedicated solely to performing the specific functions of the core. These include generating multiple lines of transgenic and knockout mice, essential for the experiments described here, as well as the performance of a variety of experimental colitis models. We will use our extensive experience in caring for large animal colonies to provide the investigators the animals they need. Centralization of these functions will allow for tight control over the genetic resources.'The minimization of variability between animals and various endpoint assays will result in fewer animals being needed to generate statistically valid results that can be compared across different studies within the PPG. The existence of this Core will also eliminate the need for each investigator to spend their time working with the animals. Aim 1: To generate multiple lines of transgenic and knockout mice Aim 2: To backcross and intercross genetically engineered mice. Aim 3: To assist with the execution of the different models of experimental colitis. Aim 4: To sacrifice the mice at the end of each study and perform necropsies to collect the appropriate tissues and organs to be analyzed by the Pathology Core.